Heat transfer unit

ABSTRACT

A heat transfer unit includes: an electrical component casing defining an internal space, the internal space housing a transformer together with a control board and a power supply board; and a cooling unit which cools an electronic component on the power supply board during operation of a compressor.

BACKGROUND

The present disclosure relates to a heat transfer unit.

A refrigeration apparatus including a refrigerant circuit has been known in the art, and has been widely used for an air conditioning system and other systems.

Japanese Unexamined Patent Publication No. H08-285331 discloses an air conditioning system that adjusts the indoor temperature. The air conditioning system includes an outdoor unit provided with an electrical component casing. The electrical component casing houses therein electrical components for operating a compressor and other devices. Specifically, the electrical component casing houses a control board and a power supply board (an inverter board).

SUMMARY

At the beginning of operation of an air conditioning system (a refrigeration apparatus), an electrical component casing of an outdoor unit (a heat transfer unit), for example, may have an extremely low internal temperature. Meanwhile, some of electronic components mounted on a control board or any other board (e.g., microcomputers and communications equipment) do not work normally at such an ambient temperature. Thus, if an attempt is made to start up a refrigeration apparatus under conditions where the air temperature around a control board or any other board is extremely low, such electronic components do not work normally. This unfortunately hinders the refrigeration apparatus from being started up. Such a problem becomes apparent if a refrigeration apparatus is used in a cold climate area, for example.

To address such a problem, the present inventors have discovered that heat generated from a transformer by turning the power on is used to increase the air temperature around a control board and any other board. This ensures that when the power is turned on, electronic components work normally. As a result, a refrigeration apparatus may be started up normally. However, such heat generated from the transformer may adversely affect the electronic components and other components after the refrigeration apparatus has been started up. This is because, after the refrigeration apparatus has been started up, heat generated by electronic components on a power supply board (an inverter board) or any other board of a compressor motor sufficiently increases the internal temperature of an electrical component casing. Consequently, a new problem occurs where, after the refrigeration apparatus has been started up, the heat generated from the transformer contributes to an increase in the temperature of the electronic component (e.g., a switching element) on the power supply board.

In view of the foregoing background, it is an object of the present disclosure to ensure that when the power is turned on, electronic components work normally, and to provide a refrigeration apparatus heat transfer unit which may prevent the internal temperature of an electrical component casing from excessively increasing after the power has been turned on.

The present disclosure is directed to a heat transfer unit. The heat transfer unit includes: a transformer (76) connected to a power supply (21); a control board (57, 58) to which power is supplied from the transformer (76); a power supply board (55) which supplies power from the power supply (21) to a compressor (16); an electrical component casing (30) defining an internal space (40), the internal space (40) housing the transformer (76) together with the control board (57, 58) and the power supply board (55); and a cooling unit (60) which cools an electronic component (78) on the power supply board (55) during operation of the compressor (16).

The transformer (76) is housed in the internal space (40) of the electrical component casing (30) together with the control board (57, 58) and the power supply board (55). Thus, if the transformer (76) generates heat by turning the power supply (21) on, the heat also increases the air temperature around the control board (57, 58) and the power supply board (55). This may prevent the air temperature around electronic components (55 a, 57 a, 58 a) on the control board (57, 58) and the power supply board (55) from being lower than the temperatures at which these electronic components work normally with reliability in a cold climate area, for example.

Meanwhile, operation of the compressor (16) increases the temperature of the electronic component (78) on the power supply board (55). However, the cooling unit (60) cooling the electronic component (78) may reduce the degree to which the temperature of the electronic component (78) increases, and may also reduce heat dissipation from the electronic component (78) to its surrounding air. Thus, even if heat of the transformer (76) is continuously released to the internal space (40) after the power supply (21) is turned on, the temperature of the internal space (40) may also be prevented from excessively increasing.

It is recommended that the heat transfer unit further include: a heat exchanger (15); and a fan (17) which transfers air passing through the heat exchanger (15). The electrical component casing (30) beneficially has an air inlet (47 b) and an air outlet (39), and the air outlet (39) beneficially opens toward a space (18) on a suction side of the fan (17).

After the power supply (21) is turned on, operation of the fan (17) allows negative pressure to act on the air outlet (39) communicating with the space (18) on the suction side of the fan (17). This allows air outside the electrical component casing (30) to flow through the inlet (47 b) into the internal space (40) of the electrical component casing (30). The air deprives the transformer (76) and other electronic components (55 a, 57 a, 58 a) of heat, and is then discharged through the outlet (39). This may reliably prevent the temperature of the internal space (40) of the electrical component casing (30) from excessively increasing due to the influence of heat generated by the transformer (76) after the power supply (21) is turned on.

It is recommended that at least one portion of the transformer (76) overlap with the air outlet (39) in a direction in which air passes through the air outlet (39).

Positioning the transformer (76) and the outlet (39) relative to each other as described above makes it easy for air flowing through the internal space (40) toward the outlet (39) to pass through a region surrounding the transformer (76). This allows heat of the transformer (76) to be reliably discharged to the outside of the electrical component casing (30). This may prevent heat of the transformer (76) from being convected through a region surrounding the power supply board (55) and the control board (57, 58), and may prevent the air temperature around the electronic components (55 a, 57 a, 58 a) from excessively increasing.

The control board (57, 58) and the power supply board (55) are beneficially disposed at a location other than a space between the transformer (76) and the air outlet (39).

Such a layout may prevent air that has passed through the transformer (76) and has deprived the transformer (76) of heat from passing through a region surrounding the control board (57, 58) and the power supply board (55). This may prevent the air temperature around the electronic components (55 a, 57 a, 58 a) from excessively increasing.

It is recommended that the cooling unit (60) include: a heat transfer tube (65) which is disposed outside the electrical component casing (30), and through which a refrigerant transferred by the compressor (16) flows; and a heat transfer member (66) passing through the electrical component casing (30), and being in contact with a power module (78) and the heat transfer tube (65), the power module (78) being the electronic component on the power supply board (55).

Thus, after the power supply (21) is turned on, heat of the power module (78) on the power supply board (55) is released to a refrigerant through the heat transfer member (66) and the heat transfer tube (65). This allows heat of the power module (78) to be reliably discharged to the outside of the electrical component casing (30), and may reduce the degree to which the temperature of each of the power module (78) and the internal space (40) increases.

According to the present disclosure, the transformer (76) is housed in the internal space (40) of the electrical component casing (30). Thus, after the power supply (21) is turned on, the air temperature around the electronic components (55 a, 57 a, 58 a) may be rapidly increased by using heat generated by the transformer (76). This may reliably ensure that the electronic components (55 a, 57 a, 58 a) work normally even under conditions where the air temperature around the heat transfer unit is low.

On the other hand, after the refrigeration apparatus has started up, the cooling unit (60) cools the electronic component (78) on the power supply board (55). This may prevent the temperature of the internal space (40) from excessively increasing due to the heat generated by the transformer (76).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing an entire configuration for an outdoor unit of an air conditioning system according to an embodiment.

FIG. 2 is a perspective view schematically showing an entire configuration for an electrical component casing according to an embodiment, and shows a state where a cover member is detached from the electrical component casing.

FIG. 3 is an exploded perspective view showing an essential portion of the electrical component casing.

FIG. 4 is a front view of the electrical component casing.

FIG. 5 is a cross-sectional view taken along the plane V-V shown in FIG. 2.

FIG. 6 is a cross-sectional view taken along the plane VI-VI shown in FIG. 2.

FIG. 7 is a circuit diagram showing a schematic configuration for a power converter according to an embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described in detail with reference to the drawings. Note that the following description of embodiments is merely beneficial examples in nature, and is not intended to limit the scope, application, or uses of the present disclosure.

A refrigeration apparatus according to the present embodiment is an air conditioning system that adjusts the air temperature in a room which is a target space. The air conditioning system is configured as a multiple air conditioning system, which includes a single outdoor unit (10), and a plurality of indoor units (not shown) connected to the outdoor unit (10) through communication pipes, for example. The air conditioning system includes a refrigerant circuit in which a vapor compression refrigeration cycle is performed. The air conditioning system according to the present embodiment is designed for cold climate areas where the outdoor air temperature is extremely low.

<Entire Configuration for Outdoor Unit>

The outdoor unit (10) constitutes a heat transfer unit, and is installed outdoors.

As shown in FIG. 1, the outdoor unit (10) includes an outdoor casing (11) in the shape of a vertically elongated rectangular parallelepiped. The outdoor casing (11) includes a single bottom panel (12), four side panels (13), and a single top panel (14). The side panels (13) have an air inlet (not shown). The top panel (14) has an air outlet (not shown). The outdoor casing (11) houses therein an outdoor heat exchanger (15), a compressor (16), and an outdoor fan (17).

The outdoor heat exchanger (15) is mounted on the bottom of the outdoor casing (II). The outdoor heat exchanger (15) is a so-called multiple surface fin-and-tube heat exchanger having a plurality of ventilation surfaces. The compressor (16) is disposed inside the outdoor heat exchanger (15). FIG. 1 shows the single compressor (16) for convenience. However, the compressor (16) may comprise two or more compressors. The outdoor fan (17) is disposed over the outdoor heat exchanger (15). The outdoor fan (17) is configured as a propeller fan. A space (18) on a suction side of the outdoor fan (17) is formed below the outdoor fan (17). A space (19) on a blowout side of the outdoor fan (17) is formed above the outdoor fan (17).

The outdoor casing (11) houses therein an electrical component unit (20). The electrical component unit (20) is disposed in an upper portion of the outdoor casing (11) to be laterally adjacent to the outdoor fan (17). More particularly, the electrical component unit (20) is disposed in a corner of the outdoor casing (11) between the top panel (14) and one of the side panels (13).

<Detailed Configuration for Electrical Component Unit>

A detailed configuration for the electrical component unit (20) will be described with reference to FIGS. 2-6. In the following description, terms implying any directions (“up,” “down,” “front,” “rear,” “right,” and “left”) are used herein relative to the directions indicated in FIG. 2 in principle. FIG. 2 is a perspective view of the electrical component unit (20) from which a cover member (47) is detached, as viewed from one of the side panels (13) of the outdoor casing (11). FIG. 3 is an exploded perspective view of essential components of the electrical component unit (20). FIG. 4 is a front view of the essential components, and corresponds to FIG. 3. FIG. 5 is a cross-sectional view taken along the plane V-V shown in FIG. 2. FIG. 6 is a schematic cross-sectional view taken along the plane VI-VI shown in FIG. 2.

[Electrical Component Casing]

The electrical component unit (20) includes an electrical component casing (30). The electrical component casing (30) is in the shape of a laterally elongated hollow substantially rectangular parallelepiped. The electrical component casing (30) includes a box-shaped casing body (31) having only its front side open, and a cover member (47) designed to close the open front side of the casing body (31) (see FIG. 3).

The casing body (31) includes a top plate (32), a bottom plate (33), a rear plate (34), a right plate (35), and a left plate (36).

The top plate (32) extends laterally along the rear plate (34). A first duct (37) and a second duct (38) are mounted on an upper surface of the top plate (32). The first duct (37) is somewhat closer to the right end of the top plate (32). The second duct (38) is disposed at substantially the center of the top plate (32). Each duct (37, 38) is formed in the shape of a rectangular cylinder having an axis extending in the front-to-rear direction. A rear opening of the duct (37, 38) communicates with the blowout-side space (19). A front opening of the duct (37, 38) communicates with a front space (46) (see FIG. 6).

The bottom plate (33) extends laterally along the rear plate (34). A substantially right half portion (33 a) of the bottom plate (33) has a plurality of air outlets (39). The outlets (39) each have a rectangular shape elongated in the front-to-rear direction. The outlets (39) are spaced uniformly in the lateral direction to be parallel to one another. Each outlet (39) opens toward the suction-side space (18) below the outdoor fan (17). The outlets (39) allow an internal space (40) of the electrical component casing (30) to communicate with the suction-side space (18) (see FIG. 6). The bottom plate (33) may be designed such that its portion (33 a) having the air outlets (39) and its remaining portion (33 b) are separate from each other.

The cover member (47) shown in FIG. 3 is removably attached to the open side of the casing body (31). A rightward portion of the cover member (47) has a swelling portion (47 a) that swells along a cooling heat transfer tube (65). An upper portion of the cover member (47) has a plurality of air inlets (47 b). The inlets (47 b) allow the front space (46) to communicate with the internal space (40) of the electrical component casing (30).

[Mounting Plate and Support Plate]

As shown in FIG. 3, the electrical component unit (20) includes a mounting plate (41), a first support plate (51), and a second support plate (52). The mounting plate (41), the first support plate (51), and the second support plate (52) are housed in the internal space (40) of the electrical component casing (30).

The mounting plate (41) is fixed to the casing body (31) so as to be located behind the cover member (47). The mounting plate (41) is formed in the shape of a plate extending horizontally from a laterally central portion of the casing body (31) to the right end thereof. An upper portion of the mounting plate (41) has two air circulation openings (42, 43). The two circulation openings (42, 43) include a first circulation opening (42) closer to the right end of the mounting plate (41), and a second circulation opening (43) closer to the left end of the mounting plate (41). Each circulation opening (42, 43) is configured as a laterally elongated, substantially rectangular hole. The circulation openings (42, 43) allow the inlets (47 b) to communicate with the internal space (40) (see FIG. 6).

A lower portion of the mounting plate (41) has a first through hole (44) and a second through hole (45). The first through hole (44) is closer to the right end of the mounting plate (41) while the second through hole (45) is closer to the left end of the mounting plate (41). Each through hole (44, 45) is configured as a laterally elongated, substantially rectangular hole. First and second cooling plates (63) and (64) of a cooling unit (60) are respectively fitted into the first and second through holes (44) and (45).

The first and second support plates (51) and (52) are supported by the mounting plate (41) between the rear plate (34) of the electrical component casing (30) and the mounting plate (41). The first support plate (51) is closer to the right end of the casing body (31) while the second support plate (52) is disposed in a laterally central portion of the casing body (31). Each support plate (51, 52) is a laterally elongated plate member.

An inverter board (55) is attached to a surface of the first support plate (51) (closer to the casing body (31)). The first support plate (51) has a back surface (closer to the cover member (47)) having an opening through which a power module (78) is to be exposed. A first heat sink (61) of the cooling unit (60) is attached to the back surface of the first support plate (51).

Fan power supply boards (56) are attached to a surface of the second support plate (52). The second support plate (52) has a back surface having openings through each of which an electronic component or any other component of an associated one of the fan power supply boards (56) is to be exposed. A second heat sink (62) of the cooling unit (60) is attached to the back surface of the second support plate (52).

[Printed Board]

As shown in FIGS. 3-6, the electrical component unit (20) includes a plurality of printed boards (55, 56, 57, 58, 59). The printed boards (55, 56, 57, 58, 59) are housed in the internal space (40) of the electrical component casing (30). Specifically, the inverter board (55), the fan power supply boards (56), the main control board (57), the auxiliary control board (58), the noise filter mounting board (59), and other boards are housed in the electrical component casing (30). In each of the drawings, various types of electronic components and other components mounted on the printed boards (55, 56, 57, 58, 59) are generally omitted.

As shown in FIGS. 3 and 5, the inverter board (55) is attached to the surface of the first support plate (51) (closer to the casing body (31)). Power from a power supply (21) is supplied to the inverter board (55). Specifically, the inverter board (55) constitutes a power supply board that supplies electric power to a motor (22) of the compressor (16). The inverter board (55) is provided with an inverter circuit (75) which will be described below in detail. Electronic components (55 a) such as a microcomputer and communications equipment are mounted on a surface of the inverter board (55) (closer to the casing body (31)). Moreover, the power module (78) is mounted on a back surface of the inverter board (55) (closer to the cover member (47)) (see FIG. 6). The power module (78) is formed in the shape of a flat rectangular parallelepiped. The power module (78) is designed such that switching elements (75 a) of the inverter circuit (75) are encapsulated in a package made of an insulating resin.

As shown in FIG. 4, the fan power supply boards (56) are attached to a surface of the second support plate (52). The fan power supply boards (56) are each provided with a power supply circuit for supplying electric power to the motor (22) of the outdoor fan (17). An electronic component (56 a) such as a microcomputer and communications equipment is mounted on each fan power supply board (56).

The main control board (57) and the auxiliary control board (58) are attached to the rear plate (34) of the electrical component casing (30). Specifically, the control boards (57, 58) are disposed at the upper left corner of the rear plate (34). The bottom plate (33) of the casing body (31) has a portion (33 b) which is located under the control boards (57, 58) and which is devoid of the outlets (39). Power from the power supply (21) is supplied through a transformer (76) to the control boards (57, 58). Specifically, the control boards (57, 58) form a control circuit (77) to be supplied with power from the power supply (21) the output voltage of which has been transformed (lowered) by the transformer (76). Electronic components (57 a, 58 a) such as a microcomputer and communications equipment are respectively mounted on the main control board (57) and the auxiliary control board (58).

The noise filter mounting board (59) is attached to a laterally central portion of the rear plate (34) of the casing body (31).

[Reactor and Transformer]

As shown in FIGS. 3 and 5, the electrical component unit (20) includes a reactor (73) and the transformer (76). The reactor (73) and the transformer (76) are housed in the internal space (40) of the electrical component casing (30).

Specifically, the reactor (73) is attached to the first heat sink (61). That is to say, a right portion of the first heat sink (61) extends rightward beyond the first support plate (51) (see FIG. 3). The reactor (73) is attached to a surface of an extending portion (61 a) of the first heat sink (61) (closer to the casing body (31)). The reactor (73) is disposed near the first circulation opening (42). Moreover, at least portions of the reactor (73) overlap with some of the outlets (39) in the vertical direction (i.e., the direction in which air passes through the outlets (39)) (see FIG. 5). Thus, the reactor (73) is disposed to at least partially extend over an air flow path (see, for example, the broken-line arrow shown in FIG. 5) formed between the inlets (47 b) or the first circulation opening (42) and the outlets (39) in the internal space (40). This allows the reactor (73) to more effectively dissipate heat through the air flowing through the internal space (40).

The transformer (76) is attached to a corner portion of the rear plate (34) of the casing body (31) defined between the top plate (32) and the right plate (35). Thus, the transformer (76) is located to the right of the inverter board (55) and the first circulation opening (42) and over the reactor (73). More particularly, the transformer (76) is disposed near the first circulation opening (42). Moreover, at least portions of the transformer (76) overlap with some of the outlets (39) in the vertical direction (i.e., the direction in which air passes through the outlets (39)). Thus, the transformer (76) is disposed to at least partially extend over an air flow path (see, for example, the broken-line arrow shown in FIG. 5) formed between the inlets (47 b) or the first circulation opening (42) and the outlets (39) in the internal space (40). This allows the transformer (76) to more effectively dissipate heat through the air flowing through the internal space (40).

The inverter board (55), the fan power supply boards (56), the main control board (57), the auxiliary control board (58), and the noise filter mounting board (59) are arranged neither between the reactor (73) and the outlets (39) nor between the transformer (76) and the outlets (39). In other words, all of the printed boards, which include the inverter board (55) and the control boards (57, 58), are disposed at a location other than a space between the reactor (73) and the outlets (39). Moreover, all of the printed boards, which include the inverter board (55) and the control boards (57, 58), are disposed at a location other than a space between the transformer (76) and the outlets (39). This may reliably prevent air that has passed through a region close to the reactor (73) and the transformer (76) from passing through the printed boards (55, 56, 57, 58, 59).

[Cooling Unit]

The electrical component unit (20) includes a cooling unit (60) for cooling various types of components in the internal space (40) of the electrical component casing (30) during operation of the air conditioning system or during operation of the compressor (16). As shown in FIGS. 2-4 and 6, the cooling unit (60) includes the first and second heat sinks (61) and (62), the first and second cooling plates (63) and (64), and the cooling heat transfer tube (65). The first heat sink (61) and the first cooling plate (63) form a first heat transfer member (66). The second heat sink (62) and the second cooling plate (64) form a second heat transfer member (67).

The first and second heat sinks (61) and (62) are each configured as a substantially plate-like member with a high thermal conductivity. The first heat sink (61) is disposed near the back surface of the first support plate (51) to be in close contact with a surface of the power module (78) on the inverter board (55). A basal portion of the reactor (73) is in close contact with the extending portion (61 a) of the first heat sink (61). The second heat sink (62) is disposed near the back surface of the second support plate (52) to be in close contact with the electronic components and other components on the fan power supply boards (56).

The first and second cooling plates (63) and (64) are each configured as a flat member with a high thermal conductivity. The first cooling plate (63) is tightly fixed to the first heat sink (61) while the second cooling plate (64) is tightly fixed to the second heat sink (62). The first and second cooling plates (63) and (64) each have a front surface having two grooves (68). These grooves (68) extend horizontally across the width of each cooling plate (63, 64). A vertical cross section of each groove (68) is substantially arc-shaped.

The cooling heat transfer tube (65) is connected to, for example, a high-pressure line of the refrigerant circuit. The cooling heat transfer tube (65) includes two straight portions (65 a) parallel to each other, and a U-shaped portion (65 b) joining the two straight portions (65 a) together at their one ends. The two straight portions (65 a) of the cooling heat transfer tube (65) are each tightly fitted to associated ones of the grooves (68) of the cooling plates (63, 64).

The cooling unit (60) exchanges heat between a refrigerant flowing through the cooling heat transfer tube (65) and the power module (78) on the inverter board (55) when the compressor (16) starts up. Moreover, the cooling unit (60) exchanges heat between the refrigerant flowing through the cooling heat transfer tube (65) and the electronic components and other components on the fan power supply boards (56). Thus, the power module (78) on the inverter board (55) and the electronic components and other components on the fan power supply boards (56) are cooled by a refrigerant flowing through the refrigerant circuit.

[Power Converter]

Next, a schematic configuration for a power converter (70) for driving the motor (22) of the compressor (16) will be described with reference to FIG. 7.

The power converter (70) is connected to the alternating power supply (21). The power converter (70) includes a power supply circuit (71), the control circuit (77). and the transformer (76) connected between the power supply circuit (71) and the control circuit (77).

The power supply circuit (71) includes four diodes (72 a), the reactor (73), and a capacitor (74). The four diodes (72 a) connected in a bridge configuration form a converter circuit (72) (a diode bridge circuit). The reactor (73) is connected to a positive output node of the converter circuit (72). The capacitor (74) is connected between the positive output node and a negative output node of the converter circuit (72).

The power supply circuit (71) includes the inverter circuit (75) that converts the output of the converter circuit (72) into three-phase alternating current to supply the three-phase alternating current to the motor (22). The inverter circuit (75) includes three switching legs each including two of the switching elements (75 a) connected in series. In the switching legs, midpoints between the upper-arm switching elements (75 a) and the lower-arm switching elements (75 a) are connected to coils of respective phases of the motor (22). The inverter circuit (75) converts a direct current voltage into a three-phase alternating current voltage by on/off operations of the switching elements (75 a), and supplies the three-phase alternating current voltage to the motor (22). The switching elements (75 a) are encapsulated in the power module (78) described above.

The transformer (76) lowers the output voltage of the power supply (21), and supplies power from the power supply (21), the output voltage of which has been lowered, to the control circuit (77). The control circuit (77) switches the switching elements (75 a) between on and off states to perform a pulse width modulation (PWM) control.

<Operation>

First, how the air conditioning system basically operates will be described. During operation of the air conditioning system, the compressor (16) and the outdoor fan (17) work. and a refrigeration cycle is performed in the refrigerant circuit. For example, in the refrigerant circuit during a cooling operation, a refrigerant compressed by the compressor (16) dissipates heat or condenses in an outdoor heat exchanger (15). The refrigerant that has dissipated heat or condensed is decompressed at an expansion valve, and then evaporates in an indoor heat exchanger. In the refrigerant circuit during a heating operation, a refrigerant compressed by the compressor (16) dissipates heat or condenses in the indoor heat exchanger. The refrigerant that has dissipated heat or condensed is decompressed at the expansion valve, and then evaporates in the outdoor heat exchanger (15).

In the outdoor unit (10) shown in FIG. 1, outdoor air passes through the inlet of the outdoor casing (11), and passes through the outdoor heat exchanger (15). The outdoor heat exchanger (15) exchanges heat between a refrigerant and outdoor air. The air that has passed through the outdoor heat exchanger (15) flows through the suction-side space (18) and the blowout-side space (19) in this order, and is ejected upward and outward of the outdoor casing (11) through the outlet thereof.

<Operation to Be Performed When Power Is Turned ON>

The outdoor unit (10) according to the present embodiment is disposed outdoors in a cold climate area. Thus, before the beginning of operation of the air conditioning system, the electrical component casing (30) may have an extremely low internal temperature (e.g., −30° C.). If the compressor (16) is started up to start up the air conditioning system under such conditions, the ambient temperature around the electronic components (55 a, 56 a, 57 a, 58 a) on the inverter board (55), the fan power supply boards (56), the main control board (57), the auxiliary control board (58), and other boards may be lower than the temperatures which ensure that the electronic components (55 a, 56 a, 57 a, 58 a) work normally. This may prevent the compressor (16) and the outdoor fan (17) from being started up normally.

To address this problem, in the present embodiment, the transformer (76) is disposed in the internal space (40) of the electrical component casing (30). That is to say. if the power supply (21) is turned on in accordance with an instruction to operate the air conditioning system, the power supply (21) and the transformer (76) are first energized. Consequently, in the electrical component unit (20), the transformer (76) operates earlier than other components, and heat is generated from the transformer (76). At this timing, as a matter of course, the compressor (16) and the outdoor fan (17) do not enter into a steady state operation yet.

If heat is generated by the transformer (76) as described above, the heat moves through the internal space (40) by convection. This increases the ambient temperature around the electronic components (55 a, 56 a, 57 a, 58 a) by a predetermined temperature (e.g., 5° C.). Consequently, in the present embodiment, when the air conditioning system is started up, the ambient temperature reliably falls within the range of temperatures at which the electronic components (55 a, 56 a, 57 a, 58 a) work normally. As a result, the electronic components (55 a, 56 a, 57 a, 58 a) may be operated normally, and the compressor (16) and the outdoor fan (17) may, in turn, be operated normally.

<Operation to Be Performed After Startup>

If the compressor (16) and the outdoor fan (17) start up, and the air conditioning system enters into a steady state operation, heat is generated from the electronic components inside the electrical component casing (30). In particular, for example, in the inverter board (55), heat is released from the power module (78) along with operation of the switching elements (75 a). This increases the temperature of the internal space (40) of the electrical component casing (30).

Meanwhile, even if the air conditioning system enters into the steady state operation as described above, heat is still released from the transformer (76). For this reason, after the startup of the air conditioning system, the influence of heat from the transformer (76) may excessively increase the temperature of the internal space (40) of the electrical component casing (30).

To address this problem, in the present embodiment, the cooling unit (60) reduces the degree to which the temperature of the internal space (40) increases. If the air conditioning system first enters into the steady state operation, and a refrigeration cycle is performed in the refrigerant circuit, a refrigerant flows through the cooling heat transfer tube (65). Thus, the power module (78) on the inverter board (55) and the electronic components and other components on the fan power supply boards (56) are cooled by the refrigerant.

More particularly, if heat is generated from the power module (78) on the inverter board (55), the heat is transferred to the first heat sink (61), the first cooling plate (63), and the straight portions (65 a) of the cooling heat transfer tube (65) in this order, and is released to the refrigerant flowing through the straight portions (65 a). This allows the heat generated from the power module (78) to be released to the outside of the electrical component casing (30) and, in turn, to the outside of the outdoor casing (11).

Moreover, if heat is generated from the electronic components and other components on the fan power supply boards (56), the heat is transferred to the second heat sink (62), the second cooling plate (64), and the straight portions (65 a) of the cooling heat transfer tube (65) in this order, and is released to the refrigerant flowing through the straight portions (65 a). This allows the heat generated from the electronic components and other components on the fan power supply boards (56) to be released to the outside of the electrical component casing (30) and, in turn, to the outside of the outdoor casing (11).

In addition, in the present embodiment, if the air conditioning system enters into a steady state operation, the air transferred by the outdoor fan (17) reduces the degree to which the temperature of the internal space (40) increases, as shown in FIGS. 5 and 6. That is to say, if the outdoor fan (17) starts up, negative pressure is generated in the space (18) on the suction side of the outdoor fan (17), while positive pressure is generated in the space (19) on the blowout side of the outdoor fan (17). The outlets (39) of the bottom plate (33) of the electrical component casing (30) open toward the suction-side space (18) that is a negative pressure space. Thus, an air flow is generated in the internal space (40) by sucking air near the outlets (39) into the internal space (40).

Specifically, air in the blowout-side space (19) first passes through the first and second ducts (37) and (38), and flows out to the front space (46) in front of the electrical component casing (30). The air in the front space (46) flows into the internal space (40) through the inlets (47 b) and the first and second circulation openings (42) and (43). The air in the internal space (40) flows downward toward the outlets (39).

More particularly, the air that has flowed downward from the first circulation opening (42) passes through a region surrounding the inverter board (55). The air is used to dissipate heat from the electronic components (55 a) on the inverter board (55) and the power module (78), and then flows out through the outlets (39) to the suction-side space (18). Moreover, the air that has flowed laterally from the first circulation opening (42) toward the transformer (76) passes through the transformer (76) and the reactor (73) in this order, and is used to dissipate heat from the transformer (76) and the reactor (73). The air that has deprived the transformer (76) and the reactor (73) of heat flows out through the outlets (39) to the suction-side space (18) without passing through the other printed boards (55, 56, 57, 58).

The air that has flowed downward from the second circulation opening (43) passes through a region surrounding the fan power supply board (56). The air is used to dissipate heat from the electronic components (56 a) on the fan power supply boards (56), and then flows out through the outlets (39) to the suction-side space (18).

Advantages of Embodiment

In the foregoing embodiment, if the power supply (21) is turned on in accordance with an instruction to operate the air conditioning system, the transformer (76) housed in the internal space (40) of the electrical component casing (30) works. As a result, heat of the transformer (76) may increase the ambient temperature around the electronic components (55 a, 56 a, 57 a, 58 a) on the printed boards (55, 56, 57, 58). This may ensure that the electronic components (55 a, 56 a, 57 a, 58 a) work normally. Thus, the compressor (16) and the outdoor fan (17) may be reliably started up.

On the other hand, if the air conditioning system enters into a steady state operation, the cooling unit (60) cools the power module (78). Thus, heat of the power module (78) may be released to the outside of the electrical component casing (30). This may prevent the temperature of the internal space (40) from increasing due to the heat generated by the transformer (76).

In addition, if the air conditioning system enters into a steady state operation, air transferred by the outdoor fan (17) flows through the internal space (40). Thus, heat of the internal space (40) may be released to the outside. This may prevent the temperature of the internal space (40) from increasing due to the heat generated by the transformer (76).

In this configuration, the transformer (76) overlaps with some of the outlets (39) in the direction in which air passes through the outlets (39). This makes it easy for the air flowing through the internal space (40) to pass through the transformer (76). This allows the transformer (76) to more effectively dissipate heat. The air that has passed through the transformer (76) and the reactor (73) is located so as to be prevented from passing through the printed boards (55, 56, 57, 58, 59). This may prevent heat of the transformer (76) and the reactor (73) from excessively increasing the air temperature around the printed boards (55, 56, 57, 58, 59).

Other Embodiments

The foregoing embodiment may also be configured as follows.

The cooling unit (60) according to the foregoing embodiment cools the power module (78) with a refrigerant flowing through the refrigerant circuit. However, the cooling unit (60) may also cool the power module (78) with air transferred by the outdoor fan (17) or any other fan, for example.

In the foregoing embodiment, heat of the transformer (76) increases the air temperature around the electronic component (55 a) on the inverter board (55), which is a power supply board. However, heat of the transformer (76) may increase the air temperature around a power supply board including a converter circuit, for example.

The heat transfer unit according to the foregoing embodiment is the outdoor unit of the air conditioning system. However, the heat transfer unit may be one of the indoor units installed indoors. Alternatively, the heat transfer unit may also be, for example, a refrigerator cooling its internal space, a so-called chilling unit, or a heat source unit for a water heater and other devices.

As can be seen from the foregoing description, the present disclosure is useful for a heat transfer unit. 

What is claimed is:
 1. A heat transfer unit comprising: a transformer connected to a power supply; a control board to which power is supplied from the transformer; a power supply board which supplies power from the power supply to a compressor; an electrical component casing defining an internal space, the internal space housing the transformer together with the control board and the power supply board; and a cooling unit which cools an electronic component on the power supply board during operation of the compressor.
 2. The heat transfer unit of claim 1, further comprising: a heat exchanger; and a fan which transfers air passing through the heat exchanger, wherein the electrical component casing has an air inlet and an air outlet, and the air outlet opens toward a space on a suction side of the fan.
 3. The heat transfer unit of claim 2, wherein at least one portion of the transformer overlaps with the air outlet in a direction in which air passes through the air outlet.
 4. The heat transfer unit of claim 2, wherein the control board and the power supply board are disposed at a location other than a space between the transformer and the air outlet.
 5. The heat transfer unit of claim 1, wherein the cooling unit includes: a heat transfer tube which is disposed outside the electrical component casing, and through which a refrigerant transferred by the compressor flows; and a heat transfer member passing through the electrical component casing, and being in contact with a power module and the heat transfer tube, the power module being the electronic component on the power supply board.
 6. The heat transfer unit of claim 3, wherein the control board and the power supply board are disposed at a location other than a space between the transformer and the air outlet.
 7. The heat transfer unit of claim 2, wherein the cooling unit includes: a heat transfer tube which is disposed outside the electrical component casing, and through which a refrigerant transferred by the compressor flows; and a heat transfer member passing through the electrical component casing, and being in contact with a power module and the heat transfer tube, the power module being the electronic component on the power supply board.
 8. The heat transfer unit of claim 3, wherein the cooling unit includes: a heat transfer tube which is disposed outside the electrical component casing, and through which a refrigerant transferred by the compressor flows; and a heat transfer member passing through the electrical component casing, and being in contact with a power module and the heat transfer tube, the power module being the electronic component on the power supply board.
 9. The heat transfer unit of claim 4, wherein the cooling unit includes: a heat transfer tube which is disposed outside the electrical component casing, and through which a refrigerant transferred by the compressor flows; and a heat transfer member passing through the electrical component casing, and being in contact with a power module and the heat transfer tube, the power module being the electronic component on the power supply board. 